The present invention generally relates to aircraft cargo doors and, more particularly, relates to an electrical control and warning indication system for use with an aircraft cargo door that employs and a method of using the same.
According to the Federal Aviation Administration (FAA), the certification requirements of warning systems on outwardly opening cargo doors state that erroneous closed, latched, and locked indication (i.e., the loss of indication) must be shown to be xe2x80x9cimprobablexe2x80x9d, which generally means having a probability of occurrence of less than or equal to 1 per 100,000 flights. Although the current text of the rules do not explicitly require it, it has recently been required by regulatory agencies that the manufacturer of airplanes with outwardly opening cargo doors demonstrate that nuisance indication is also xe2x80x9cimprobable.xe2x80x9d In addition, regulatory agencies have expended significant effort to reduce occurrences of unnecessary rejected takeoffs resulting from nuisance warning indications.
It has been possible to meet, although marginally, the improbable erroneous indication requirements with existing single channel indication systems. However, it has not always been possible to meet the requirements that nuisance indication also be improbable. In the instances where it was not possible to comply fully with the nuisance indication requirement, the regulatory agencies involved have noted the difficulty in meeting this requirement and have accepted this limitation.
With reference to single channel systems, it is not generally possible to determine if a warning is accurate, or not, nor has it been possible to reduce the probability of both erroneous and nuisance indication. Because of these limitations, significant reductions in the occurrence of rejected takeoffs due to false cargo door indications have not been realized.
The indication systems on outwardly opening, cargo doors having cam-type latches have historically been single channel systems. Because of this, these single channel systems have not been able to determine if the closed, latched, or locked status of the cargo door is erroneous or not. Therefore, if either of the closed, latched, or locked state of the cargo door should transition to the inverse state, a warning message must be provided. If this indication is erroneous, and occurs during the takeoff roll, a risky heavy weight rejected takeoff must be performed.
Closed, latched, and locked status indications of a cargo door is often provided at a cargo door operator""s control panel near the cargo door opening. An example of such an indication system is provided in U.S. Pat. No. 5,735,487, commonly owned herewith, the disclosure of which is incorporated herein by reference. However, known control panels have not incorporated features to deactivate the warnings if faults are detected prior to flight and the airplane is being dispatched per Minimum Equipment List conditions with the warning system working improperly.
Accordingly, there exists a need in the relevant art to provide visual and aural warning indications relative to the safety status of an outwardly opening cargo door on transport category airplanes. Moreover, there exists a need in the relevant art to provide a warning indication system that is capable of distinguishing whether a warning indication is false, thereby reducing the occurrence of unnecessary rejected takeoffs. Furthermore, there exists a need in the relevant art to provide a warning indication system that overcomes the disadvantages of the prior art systems.
According to the principles of the present invention, a cargo door electrical control and warning indication system having an advantageous construction and method of use is provided. The warning indication system is adapted for use with a cargo door of an aircraft. The cargo door being positionable in an opened position; a closed position; a closed and latched position; and a closed, latched, and locked position. The method includes outputting first and second closed signals when the cargo door is in the closed position; outputting first and second latched signals when the cargo door is in the closed and latched position; and outputting first and second locked signals when the cargo door is in the closed, latched, and locked position. All of the signals are then analyzed to positively determine the position of the cargo door, while minimizing the probability of false indications. Various warnings are generated in response to the combination of signals received. The apparatus employs a dual logic system and redundant sensors to provide differing warnings dependent on the phase of flight.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.